Conventional gas turbine engine high pressure rotor designs routinely incorporate bolted flanges within and between compressor and turbine rotors to facilitate assembly and maintenance activities performed on the engine. Such connections provide varying degrees of engine modularity, whereby entire modules of an engine may be removed and replaced readily without extensive teardown of associated components. Such modularity supports rapid replacement of modules containing damaged or life limited hardware and is a highly desirable feature from a maintainability perspective. A significant limitation imposed by such designs, however, is the added weight, cost and complexity of such connections, especially in rotating components which operate at high rotational speeds in elevated temperature environments. For example, bolt holes form stress concentration zones which oftentimes are a life limiting feature of a costly compressor spool or turbine disk. Further, the added weight of bolted flange assemblies slows the thermal and inertial response of the rotor as well as increases bearing loads requiring highly complex, damped bearing systems to provide acceptable operational dynamics, especially during periods of severe imbalance such as occurs after loss of a compressor or turbine blade.
An alternative, lighter rotor design incorporates a plurality of compressor and turbine components, for example, integrally bladed disks commonly referred to as blisks, spools and disks with removeable blading, and spacer shafts, connected in rotational driving engagement by radial face splines, typically referred to as Curvic couplings, or other non-bolted connections such as rabbets. A single shaft may span solely a compressor or turbine rotor or alternatively an entire gas generator rotor assembly, applying a compressive load therethrough to prevent separation of the compressor and turbine components and related hardware. Due to the nature of a single shaft rotor system, the assembled integrity of which is maintained solely by compressive loading applied by the rotor shaft, maintenance activity performed on the rotor or modules through which the rotor passes is typically more complex than in engines having bolted flanged rotors. Extensive disassembly of unrelated hardware may be required before a target component, such as an annular combustor liner, can be accessed and replaced. In an effort to reduce such effort, special tooling can be designed and attachment features provided on the rotor and stationary frame structure of the engine to mechanically support a portion of the rotor, permitting partial disassembly thereof. In this manner, for example, the mechanical integrity of the compressor rotor can be maintained while the turbine is disassembled. Such tooling systems add cost and complexity to the user support requirements of the engine. In addition to requiring attachment features in the engine, often in high value rotor components, design constraints are imposed since unrestricted clearance and access volumes must be maintained through which such tooling passes. Further, the opportunity exists for damage to costly rotor components and proximate hardware whenever such tooling is utilized either through improper use or inadvertent contact resulting in component surface distress.